Determining your electrical needs
If you’re going to the expense of adding a workshop or studio to your property, you’re likely to spend a fair amount of time using it. That’s one reason to wire it much as if it’s your primary living space.
“I’d recommend having at least the minimal number of outlets you would have inside the house,” says Shane Grasser, an electrical contractor in St. Peters, Mo. Most building codes require one outlet every 12 feet at minimum.
Grasser also suggests installing the lighting you think you need and then a bit more. “I’d recommend adding as much lighting as you can put in it. You can always turn lights off,” he says. “It’s never going to hinder you to put in additional outlets and lighting. It can only benefit you.”
Sound extravagant? Not really. Once an electrician is on site to do the essential wiring, adding another device is literally the work of a few minutes. For instance, adding a receptacle costs about $10 in labor and the same amount in materials. Add the same receptacle after the drywall is on and the cost could be 10 times as much.
Plan in plenty of the basics, then consider these add-ons to suit special uses:
- Woodworking or machine shop: 220-volt receptacles, extra task lighting, paint area ventilation, 4-gang 110-volt receptacles for a recharging center, baseboard heat.
- Office: Plenty of receptacles near the computer area equipped with built-in surge protection, baseboard heat, Internet cable access, phone access.
- Ceramics studio: Adjustable overhead lighting, 220-volt wiring for an electrical kiln, ventilation fan, baseboard heat, GFCI receptacles for cleanup areas.
- Painter’s studio: Color-corrected fluorescent lighting (a 3500 to 4000 Kelvin rating is often preferred), built-in ventilation fans, extra receptacles for small shop area for stretching canvases, baseboard heat, GFCI receptacles in clean-up area.
- Getaway retreat: Indirect lighting, phone access (or not), Internet and television cable access.
- Small business headquarters: A second meter and breaker panel to keep utility costs separate.
Getting power to your structure
Unless you’re in a rural area, you’ll be required to run a buried line, a wise choice under any circumstances to avoid an eyesore and potential power outage due to downed lines. The cost of trenching and laying underground conduit runs about $1,000. Because most of the expense is in getting the trenching machinery to site, the cost won’t vary substantially whether you need a 25- or a 100-foot trench.
If you have open circuits in your household breaker panel, you can run lines directly to your new building without installing a panel. However, adding a subpanel makes the most sense.
“I always recommend a subpanel because it gives you the most flexibility for the future,” says Grasser. “It gives you the ability to have 220-volt circuits, dedicated circuits for machinery, whatever you might need.” Plan on about $700 for an installed 100-amp subpanel with 20 breakers, including pulling and connecting cable from the house.
Wiring the building
Grasser emphasizes that the basic $2,500 to $3,500 cost of wiring an outbuilding can include a few 220-volt circuits for special use. Installing a 220-volt circuit is only moderately more expensive than installing a 110-volt circuit.
Beyond the essentials, here are the installed costs of some additional features:
- Four 1500-watt, thermostatic-controlled baseboard heaters (to heat a 600 sq. ft. space), $400-$600
- Hotel-style in-wall heat and A/C unit: $1,000
- Built-in thermostatically controlled wall or attic ventilation: $500–$600
- Surge protection at subpanel: $250
- Second in-ground conduit for low-voltage wiring (cable, Internet, etc.): $100
- Three-way switch in the house to control an outdoor light on the new structure: $200
What you can do to save money
Wiring is best left to the pros, but here are some do-it-yourself chores to spare the budget:
- Dig the trench yourself. The required depth is 18 to 40 inches depending on your locale. (Tip: Depth is measured from the top of the conduit, not the bottom of the trench.) You’ll have to arrange for an inspection before burying the conduit. Potential savings after purchase of underground conduit: $900.
- Prepare a clean site. Stored items and piled lumber makes it harder for the electricians to do their work efficiently. “If it is wide open and easy to work in and nothing is in the guys’ way, the price is going to be cheaper,” Grasser advises. Potential savings: $400.
- Plan ahead. A little extra expense now can save big bucks later. For example, running underground conduit for low-voltage lines adds about $100, whether you need them now or not. Potential savings: $1,000 to trench in low-voltage lines later.
- Upgrade fixtures later. A serviceable light fixture can cost less than $50—a designer fixture costs $200 and up. The illumination is the same.
Zoning and building codes
Many residential areas are zoned for single-family occupancy and prohibit renting or leasing a portion of the property to another individual or family. They may impose limitations of how your structure is wired.
Lonny Rutherford of Legacy Construction in Farmington, N.M., ran into just such a situation when planning an office structure on his property. “The city required that we tie into the utilities in our house,” he says. That meant running an underground feed from his breaker panel to a subpanel in his outbuilding; a separate meter wasn’t allowed. “They don’t want it to be metered independently so you can rent it out as an apartment.”
Code requirements are surprisingly minimal for an outbuilding. As long as the structure won’t be living space, the stipulated outlets and lights are about what you’d expect for a garage. Although the National Electric Code (NEC) is the standard from which cities formulate their codes, local differences abound, mostly in the types of cable or conduit required.
Most homeowners have a tough time interpreting local codes correctly; good reason to hire a licensed electrician. Inspections are required after trenching, when wiring and boxes are roughed in, and after drywalling when all devices are installed.